As shown in FIG. 1, certain conventional corn mill processes (1) may mill an amount of whole corn (2) into a mixture of corn particles (3) (referred to hereinafter as “milled corn”) which may include particles of corn bran (19), corn endosperm (20) and corn germ (21). Certain of the particles of corn germ (21) and corn bran (19) may have bound or have associated particles of corn endosperm (20). The milled corn (3) can be transferred to an ethanol production process (4) which includes the conventional steps of fermentation, distillation, and dehydration to generate an amount of ethanol (5). In the fermentation step, the milled corn (3) may be combined with an amount of water and an amount of alpha-amylase (or other enzyme capable of liquefying corn starch) to generate a mash in which the starch of the corn endosperm is liquefied. The mash may be held for a period of time at a temperature of between about 77 degrees Celsius (“° C.”) (about 170 degrees Fahrenheit (“° F.”) and about 100° C. (about 212° F.) to kill bacteria in the mash. The mash may then be held at a temperature of between about 32° C. (about 90° F.) and about 38° C. (about 100° F.) for a period of time sufficient to achieve a desired level of liquefaction of the starch. An amount of gluco-amylase (or other enzyme capable of generating fermentable sugars from the liquefied starch) added to the mash converts the liquefied starch to fermentable sugars, such as dextrose, in a process referred to as saccharification. Yeast can then be added to the mash and the mash held at a temperature of between about 29° C. (about 85° F.) and about 32° C. (about 90° F.) to convert the sugars to an amount of ethanol (5) and an amount of carbon dioxide (6) (or “CO2”) along with other volatile organics. The amount of carbon dioxide (6) can be stored or sold in the marketplace. For sale into certain markets or for use in certain applications, the amount of carbon dioxide (6) can be stripped of the other volatile organics and captured as an amount of purified carbon dioxide (9). The fermented mash often referred to as “beer” includes an amount of ethanol (5) in a concentration of about eight percent (“%”) to about 20% by weight, other liquids and non-fermentable solids. The amount of ethanol (5) in the beer can be separated and concentrated to about 190 proof by conventional distillation techniques and dehydrated by application to molecular sieve to produce a dehydrated ethanol (5) of about 200 proof. Ethanol (5) of about 200 proof may be combined with up to about five percent denaturant to generate an amount of fuel ethanol (10).
The stillage which remains after distillation of the beer can comprise an amount of liquid typically referred to as “thin stillage” and an amount of remaining solids typically referred to as the “distillers grains”. The thin stillage can be separated from the distillers grains (for example by centrifugation). The distillers grains can be dried by evaporation of the remaining thin stillage to produce “dried distillers grains” (“DDG”) (7). The thin stillage can be concentrated by evaporation of water to generate a syrup containing about thirty percent solids (also referred to as “condensed distiller soluble”). The syrup can be recombined with the dried distillers grains (7) to generate an amount of distillers dried grain with solubles (8) (“DDGS”). The DDGS (8) can be sold as animal feed.
Even though there is an increasing demand for fuel ethanol (10) worldwide and an increasing amount of research in ethanol production, there remain substantial unresolved problems with respect to conventional corn mill processes (1) for ethanol (5) production.
A first substantial problem with conventional corn mill processes (1) for ethanol (5) production can be that milled corn (3) introduced into the ethanol production process (4) which includes corn bran (19), corn endosperm (20) and corn germ (21) requires an amount of thermal energy (11) (or energy Btus or Btus) to complete the steps of fermentation, distillation and dehydration, and by-product handling. To generate about a gallon of fuel ethanol (10), and a corresponding amount of DDGS (8) and carbon dioxide (6) the ethanol production process (4) utilizing milled corn (3) consumes an amount of thermal energy (11) of between about 20,000 British thermal units (hereinafter “Btu”) and about 35,000 Btu (the term “about” as used herein means greater or lesser than the value or range of values stated by 10 percent, but not does not limit any value or range of values to this broader definition and each value or range of values preceded by the term “about” also includes in the alternative the stated absolute value or range of values). This amount of thermal energy (11) is typically generated by burning a corresponding amount of fossil fuel (12) such as oil, coal oil, coal, natural gas, or the like.
Inclusion of an amount of non-fermentable biomass or substantially non-fermentable biomass, such as corn bran (19) or corn germ (21), into the ethanol production process (4) requires allocation of an amount of thermal energy (11) to process the amount of non-fermentable biomass; however, this amount of non-fermentable biomass or substantially non-fermentable biomass does not produce any or produces very little ethanol (5) which increases the amount of thermal energy (11) used per unit of ethanol (5) produced as compared to an ethanol production process (4) in which only the fermentable corn endosperm (20) is processed. Because the corn bran (19) and corn germ (21) represent about 17% by weight of the milled corn (3), if the corn bran (19) and the corn germ (21) can be removed from the ethanol production process (4), than the amount of thermal energy (11) consumed by the ethanol production process (4) per unit of ethanol (4) produced may be substantially reduced.
A second substantial problem with the conventional corn mill process (1) for ethanol production (4) can be that milled corn (3) introduced into the ethanol production process (4) which includes non-fermentable biomass or substantially non-fermentable biomass requires allocation of an amount of fermenter capacity to biomass which does not produce any or produces very little ethanol (5). If the corn bran (19) and the corn germ (21) can be removed from the ethanol production process (4), then the corresponding amount of fermenter capacity freed up could be utilized to process additional fermentable biomass.
A third substantial problem with the conventional corn mill process (1) for ethanol production can be that milled corn (3) introduced into the ethanol production process (4) which includes non-fermentable biomass or substantially non-fermentable biomass increases the amount of “distillers grains” produced per unit of ethanol (5) produced. The distillers grains must be dried as above-described to produce dried distiller grains (“DDG”) (7) or dried distillers grains with solubles (“DDGS”) (8). The drying of “distillers grains” can be the single largest point of energy (11) consumption in the ethanol production process (4). If the corn bran (19) and the corn germ (21) can be removed from the ethanol production process (4), then a corresponding reduction in the amount “distillers grains” can be achieved with a corresponding reduction in the amount of thermal energy (11) utilized to produce DDG (7) per unit of ethanol (5) produced.
A fourth substantial problem with conventional corn mill processes (1) for ethanol production (4) can be that the market for conventional DDG (7) by products may become saturated as the number of ethanol production facilities increases. Conventional DDG (7) includes corn bran (19). As the amount of corn bran (19) increases in the DDG (7) the percent protein by weight decreases. As the percent protein by weight of the DDG (7) decreases the value of the DDG (7) or DDGS (8) as a feed may also decrease. Additionally, inclusion of corn bran (19) in the DDG (7) increase the fiber content of the DDG (7) which can make the DDG (7) unacceptable as a feed for poultry, fish and pet food.
Now referring primarily to FIG. 2, an alternative to the conventional corn mill process (1) can be a dry corn mill process (13) which facilitates isolation of a corn bran fraction (15), a corn germ fraction (16), and a corn endosperm fraction (14). The corn endosperm fraction (14) generated from the conventional dry corn mill process (13) can be introduced into an ethanol production process (4) above-described to in part address certain of the above-identified problems. However, because the primary function of the conventional dry corn mill process (13) is to facilitate the production of a lowered-fat grit or meal for the production of food products such as cereal, table grits or the like, the conventional dry corn mill process shown in FIG. 2 (13) including hardware and methods of utilizing the hardware have not been developed to produce a corn endosperm fraction (14) for introduction into an ethanol production process (4). Now referring to FIG. 2 and Table 1, conventional dry milling process (13) for whole corn (2) can generate a corn germ fraction (16) or a corn bran fraction (15) which still includes a substantial amount of corn endosperm (20) (reported out as “starch” in Table 5). However, loss of corn endosperm (20) to the corn germ fraction (16) or the corn bran fraction (15) solely to increase purity of the corn endosperm fraction (14) in the context of an ethanol production process (4) can result in significant economic losses.
Another substantial problem with the dry corn mill process (13) can be that the resulting corn germ fraction (16) may not contain sufficient corn oil (22) on a dry matter basis to economically enter conventional corn oil extraction processes (23). Corn germ (21) which enters conventional corn oil (22) extraction processes is typically greater than 30% corn oil (22) on a dry matter basis (“dmb”). Currently, conventional dry corm mill processes (13) produce a corn germ fraction (16) having corn oil (22) on a dmb in a range of about 15% and about 25%.
Another substantial problem with dry corn mill processes (13) can be that the resulting corn germ fraction (16) does not have a desired protein dispersibility index (“PPI”). The PDI is a measure of the total protein (24) in the corn germ fraction (16) on a dmb which can be extracted into water.
Now referring primarily to FIG. 3, the use of conventional wet corn mill process (17) has been used to address certain problems associated with the conventional dry mill process (13). In the conventional wet mill process (17), whole kernel corn (2) enters a wet mill process (18) in which the whole corn (2) enters a steep liquid (25) (typically water which can further include sulfur dioxide) for a period of between 24 and 36 hours to soften the constituent parts of the kernel of whole corn (2). The softened kernel of whole corn (2) can be ground to free the corn germ (21) from the corn bran (19) and the corn endosperm (20). Because the corn germ (21), the corn bran (19) and the corn endosperm (20) of softened whole corn (2) break away from one another more cleanly when ground, the purity of the separated corn germ fraction (16), corn bran fraction (15) and corn endosperm fraction (14) may have an increased purity on a dmb as compared to the conventional dry corn mill process (13). The corn endosperm fraction (14) can be introduced into a conventional ethanol production process (4) for the production of ethanol (5) and fuel ethanol (10), as above described.
A substantial problem with conventional wet milling process (17) may be that the quality of the whole corn (2) introduced into the conventional wet milling process (17) has to be greater than that introduced into a conventional dry milling process (13). Freeman, J. E., Quality Factors Affecting Value of Corn for Wet Milling, Trans. ASAE 16:671-678, 682 (1973); and Wang, D. and Eckhoff, S. R., Effect of Broken Corn Levels on Water Absorbtion and Steepwater Characteristics, Cereal Chem. 77:525-528 (2000), each incorporated by reference herein. Broken or cracked pieces of corn (24) mixed into the whole corn (2) must be removed by screening before the proceeding with conventional wet milling process (17) as these broken pieces of corn (24) slough off starch, sugars, and protein which enter the steep water (18) and cause gelling during evaporation of the steep water (18). Also, the increased viscosity of the steep water (18) may restrict water flow through the steeps and screens. Additionally, conventional corn wet milling consumes a great amount of water and energy generate conventional corn fractions (14) (15) (16).
The inventive dry-wet grain fractionation system addresses each of the foregoing problems of the conventional dry corn mill process and the conventional wet corn mill process.